Infrared finiteness of a complete theory of charged scalars and fermions at finite temperature

It is known that the infrared (IR) divergences accruing from pure fermion–photon interactions at finite temperature cancel to all orders in perturbation theory. The corresponding infrared finiteness of scalar thermal QED has also been established recently. Here, we study the IR behaviour, at finite temperature, of theories where charged scalars and fermions interact with neutrals that could potentially be dark matter candidates. Such thermal field theories contain both linear and sub-leading logarithmic divergences. We prove that the theory is IR-finite to all orders in perturbation, with the divergences cancelling order by order between virtual and real photon corrections, when both absorption and emission of photons from and into the heat bath are taken into account. The calculation follows closely the technique used by Grammer and Yennie for zero temperature field theory. The result is generic and applicable to a variety of models, independent of the specific form of the neutral-fermion–scalar interaction vertex.

A review of neutrino properties Neutrino oscillations - a historical overview and its projection

In a first part neutrino properties are presented from the beginnings through the letter of Wolfgang Pauli on 4. December 1930 suggesting a new neutral fermion to the “Radioactive Ladies and Gentlemen” at a Conference in Tübingen, contributing to the first oscillation cycle, based on my review at the meeting “Neutrino Telescopes in Venice” in 2005. cited in [1]. In the remaining part I shall present a selection of neutrino properties featuring the structure of mass and mixing of the light and heavy neutrino flavors, a symmetric, complex 6 by 6 matrix within the unifying SO10 gauge group, and present prospects for the detection of the leptonflavor violating processes Bs → μe; B → K μ e, also such involving b-flavored baryons .

The many guises of a neutral fermion singlet

The addition of a neutral fermion singlet to the Standard Model (SM) of particle interactions leads to many diverse possibilities. It is not necessarily a right-handed neutrino. I discuss many of the simplest and most interesting scenarios of possible new physics with this approach. In particular, I propose the possible spontaneous breaking of baryon number, resulting in the massless “sakharon”.

Gauge B–L model of radiative neutrino mass with multipartite dark matter

We propose an extension of the Standard Model of quarks and leptons to include gauge B–L symmetry with an exotic array of neutral fermion singlets for anomaly cancellation. With the addition of suitable scalars also transforming under U(1)[Formula: see text], this becomes a model of radiative seesaw neutrino mass with possible multipartite dark matter. If leptoquark fermions are added, necessarily also transforming under U(1)[Formula: see text], the diphoton excess at 750 GeV, recently observed at the Large Hadron Collider, may also be explained.